中文摘要：

等熵卸载线的研究对物态方程、冲击波在自由面的卸载等问题有重要的意义.基于流体模型假定下推导等熵线的方法,计算得到了无氧铜分别以线性和二次Hugoniot关系为参考的等熵卸载线.在P-u图中,随着初始卸载压力增大,两条等熵卸载线间偏离逐渐变大,等熵卸载线与镜像的Hugoniot线逐渐出现较大的偏离.通过与无氧铜向空气卸载实验的数据比较,采用二次Hugoniot关系为参考得到的等熵卸载线与实验结果更相符,并且自由面卸载过程近似为等熵过程分析是合理的.压力大于180GPa时,用自由面速度的1/2近似得到粒子速度的误差达5%以上,实验中试图通过测量自由面速度得到粒子速度时必须做相应的计算修正.

英文摘要：

The research of isentropic release curve is significant for equation of state（EOS）and shock wave released on the free surface of sample.In this paper,the isentropic release curves were calculated by employing linear and quadratic Hugoniot relation as the reference of Grüneisen EOS.The calculated pressure-particle graph showed that the relative deviation among two isentropic release curves and mirror reflection of the principal Hugoniot increases gradually with the releasing process and initial releasing pressure.The comparisons for OFHC copper released into air showed that the experiments can be described well by the isentropic release curves which calculated with quadratic Hugoniot relation.And it is reasonable that the process of OFHC copper released into air at free surface is approximated to isentropic release.The error of free surface velocity approximated as twice of particle velocity is larger than 5% at initial releasing pressure of 180 GPa.It is invalided at sufficiently high pressures on the Hugoniot that release behavior of OFHC copper is approximated by a simple mirror reflection of the principal Hugoniot in the pressure-particle velocity plane.